var email = "email@example.com";
var isValid = ValidateEmail(email, out string message);
if (isValid)
{
    //do something
}

        public OperationResult ValidateEmail(string email)
        {
            var result = new OperationResult();

            if (string.IsNullOrWhiteSpace(email))
            {
                result.Success = false;
                result.AddMessage("email is null.");
            }

            if (result.Success)
            {
                var isValidFormat = true;//todo: using RegularExpression
                if (!isValidFormat)
                {
                    result.Success = false;
                    result.AddMessage("email is not in a correct format");
                }
            }

            if (result.Success)
            {
                var isRealDoamin = true;//todo: Code here that confirms whether domain exists.
                if (!isRealDoamin)
                {
                    result.Success = false;
                    result.AddMessage("email does not include a valid domain.");
                }
            }

            return result;
        }

این بار خروجی متد مذکور از نوع OperationResult ای می‌باشد که هم موفقیت آمیز بودن یا عدم آن را مشخص می‌کند و همچنین امکان دسترسی به لیست پیغام‌های مرتبط با اعتبارسنجی‌های انجام شده، وجود دارد.

    [Serializable]
    public class MvcAjaxResponse : MvcAjaxResponse<object>
    {
        public MvcAjaxResponse()
        {
        }

        public MvcAjaxResponse(bool success)
            : base(success)
        {
        }

        public MvcAjaxResponse(object result)
            : base(result)
        {
        }

        public MvcAjaxResponse(ErrorInfo error, bool unAuthorizedRequest = false)
            : base(error, unAuthorizedRequest)
        {
        }
    }
   

    [Serializable]
    public class MvcAjaxResponse<TResult> : MvcAjaxResponseBase
    {
        public MvcAjaxResponse(TResult result)
        {
            Result = result;
            Success = true;
        }

        public MvcAjaxResponse()
        {
            Success = true;
        }

        public MvcAjaxResponse(bool success)
        {
            Success = success;
        }

        public MvcAjaxResponse(ErrorInfo error, bool unAuthorizedRequest = false)
        {
            Error = error;
            UnAuthorizedRequest = unAuthorizedRequest;
            Success = false;
        }

        /// <summary>
        ///     The actual result object of AJAX request.
        ///     It is set if <see cref="MvcAjaxResponseBase.Success" /> is true.
        /// </summary>
        public TResult Result { get; set; }
    }

    public class MvcAjaxResponseBase
    {
        public string TargetUrl { get; set; }

        public bool Success { get; set; }

        public ErrorInfo Error { get; set; }

        public bool UnAuthorizedRequest { get; set; }

        public bool __mvc { get; } = true;
    }

    [Serializable]
    public class EntityNotFoundException : Exception
    {
        public Type EntityType { get; set; }
        public object Id { get; set; }
        public EntityNotFoundException()
        {
        }

        public EntityNotFoundException(string message)
            : base(message)
        {

        }

        public EntityNotFoundException(string message, Exception innerException)
            : base(message, innerException)
        {
        }

        public EntityNotFoundException(SerializationInfo serializationInfo, StreamingContext context)
            : base(serializationInfo, context)
        {

        }
        public EntityNotFoundException(Type entityType, object id)
            : this(entityType, id, null)
        {

        }
        public EntityNotFoundException(Type entityType, object id, Exception innerException)
            : base($"There is no such an entity. Entity type: {entityType.FullName}, id: {id}", innerException)
        {
            EntityType = entityType;
            Id = id;
        }

    }

        public async Task<UserOrganizationalUnitInfo> GetCurrentOrganizationalUnitInfoOrNullAsync(long userId)
        {
            return (await _setting.GetSettingValueForUserAsync(
                    UserSettingNames.CurrentOrganizationalUnitInfo, userId).ConfigureAwait(false))
                .FromJsonString<UserOrganizationalUnitInfo>();
        }

using System.Collections.Generic;

namespace NHSample4.Domain
{
 public class Course
 {
     public virtual int Id { get; set; }
     public virtual string Teacher { get; set; }
     public virtual IList<Student> Students { get; set; }

     public Course()
     {
         Students = new List<Student>();
     }
 }
}

using System.Collections.Generic;

namespace NHSample4.Domain
{
 public class Student
 {
     public virtual int Id { get; set; }
     public virtual string Name { get; set; }
     public virtual IList<Course> Courses { get; set; }

     public Student()
     {
         Courses = new List<Course>();
     }
 }
}

using FluentNHibernate.Automapping;
using FluentNHibernate.Cfg;
using FluentNHibernate.Cfg.Db;
using NHibernate.Tool.hbm2ddl;

namespace NHSessionManager
{
 public class Config
 {
     public static FluentConfiguration GetConfig()
     {
         return
           Fluently.Configure()
                   .Database(
                      MsSqlConfiguration
                        .MsSql2008
                        .ConnectionString(x => x.FromConnectionStringWithKey("DbConnectionString"))                        
                       )
                     .Mappings(
                       m => m.AutoMappings.Add(
                          new AutoPersistenceModel()
                              .Where(x => x.Namespace.EndsWith("Domain"))
                              .AddEntityAssembly(typeof(NHSample4.Domain.Course).Assembly))                              
                              .ExportTo(System.Environment.CurrentDirectory)
                              );
     }

     public static void CreateDb()
     {
         bool script = false;//آیا خروجی در کنسول هم نمایش داده شود
         bool export = true;//آیا بر روی دیتابیس هم اجرا شود           
         bool dropTables = false;//آیا جداول موجود دراپ شوند
         new SchemaExport(GetConfig().BuildConfiguration()).Execute(script, export, dropTables);
     }
 }
}

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
 <!--NHSessionManager-->
 <add name="DbConnectionString"
      connectionString="Data Source=(local);Initial Catalog=HelloNHibernate;Integrated Security = true"/>
</connectionStrings>
</configuration>

using System;
using System.Linq;
using System.Linq.Expressions;

namespace NHSample4.NHRepository
{
 //Repository Interface
 public interface IRepository<T>
 {
     T Get(object key);

     T Save(T entity);
     T Update(T entity);
     void Delete(T entity);

     IQueryable<T> Find();
     IQueryable<T> Find(Expression<Func<T, bool>> predicate);
 }
}

using System;
using System.Linq;
using NHSessionManager;
using NHibernate;
using NHibernate.Linq;

namespace NHSample4.NHRepository
{
 public class Repository<T> : IRepository<T>, IDisposable
 {
     private ISession _session;
     private bool _disposed = false;

     public Repository()
     {
         _session = SingletonCore.SessionFactory.OpenSession();
         BeginTransaction();
     }

     ~Repository()
     {
         Dispose(false);
     }

     public T Get(object key)
     {
         if (!isSessionSafe) return default(T);

         return _session.Get<T>(key);
     }

     public T Save(T entity)
     {
         if (!isSessionSafe) return default(T);

         _session.Save(entity);
         return entity;
     }

     public T Update(T entity)
     {
         if (!isSessionSafe) return default(T);

         _session.Update(entity);
         return entity;
     }

     public void Delete(T entity)
     {
         if (!isSessionSafe) return;

         _session.Delete(entity);
     }

     public IQueryable<T> Find()
     {
         if (!isSessionSafe) return null;

         return _session.Linq<T>();
     }

     public IQueryable<T> Find(System.Linq.Expressions.Expression<Func<T, bool>> predicate)
     {
         if (!isSessionSafe) return null;

         return Find().Where(predicate);
     }

     void Commit()
     {
         if (!isSessionSafe) return;

         if (_session.Transaction != null &&
             _session.Transaction.IsActive &&
             !_session.Transaction.WasCommitted &&
             !_session.Transaction.WasRolledBack)
         {
             _session.Transaction.Commit();
         }
         else
         {
             _session.Flush();
         }
     }

     void Rollback()
     {
         if (!isSessionSafe) return;

         if (_session.Transaction != null && _session.Transaction.IsActive)
         {
             _session.Transaction.Rollback();
         }
     }

     private bool isSessionSafe
     {
         get
         {
             return _session != null && _session.IsOpen;
         }
     }

     void BeginTransaction()
     {
         if (!isSessionSafe) return;

         _session.BeginTransaction();
     }


     public void Dispose()
     {
         Dispose(true);
         // tell the GC that the Finalize process no longer needs to be run for this object.
         GC.SuppressFinalize(this);
     }

     protected virtual void Dispose(bool disposeManagedResources)
     {
         if (_disposed) return;
         if (!disposeManagedResources) return;
         if (!isSessionSafe) return;

         try
         {
             Commit();
         }
         catch (Exception ex)
         {
             Console.WriteLine(ex.ToString());
             Rollback();
         }
         finally
         {
             if (isSessionSafe)
             {
                 _session.Close();
                 _session.Dispose();
             }
         }

         _disposed = true;
     }
 }
}

using System;
using System.Collections.Generic;
using NHSample4.Domain;
using NHSample4.NHRepository;

namespace NHSample4
{
 class Program
 {
     static void Main(string[] args)
     {
         //ایجاد دیتابیس در صورت نیاز
         //NHSessionManager.Config.CreateDb();

      
         //ابتدا یک دانشجو را اضافه می‌کنیم
         Student student = null;
         using (var studentRepo = new Repository<Student>())
         {
             student = studentRepo.Save(new Student() { Name = "Vahid" });
         }

         //سپس یک واحد را اضافه می‌کنیم
         using (var courseRepo = new Repository<Course>())
         {
             var course = courseRepo.Save(new Course() { Teacher = "Shams" });
         }

         //اکنون یک واحد را به دانشجو انتساب می‌دهیم
         using (var courseRepo = new Repository<Course>())
         {
             courseRepo.Save(new Course() { Students = new List<Student>() { student } });
         }
      
         //سپس شماره دروس استادی خاص را نمایش می‌دهیم
         using (var courseRepo = new Repository<Course>())
         {
             var query = courseRepo.Find(t => t.Teacher == "Shams");

             foreach (var course in query)
                 Console.WriteLine(course.Id);
         }

         Console.WriteLine("Press a key...");
         Console.ReadKey();
     }
 }
}